We intend to acquire a state-of-the art circular dichroism instrument to fulfill unmet research needs in the Tampa Bay region. The proposed instrument spans the range 180 nm (noise 3 mdeg) - 700 nm (noise 0.6 mdeg). Its stopped-flow accessory will allow kinetics measurements in the millisecond range. The core users will apply it to conformational problems of protein-nucleic acid interactions, phosphorylase kinase interactions with Ca++ and Mg++, c-ribofuranosyl nucleoside derivatives, creatine kinase denaturation and renaturation, and nitrate reductase interactions. Each investigator is familiar with his own area, and has mastered the startup and preparative problems of each project. The only barrier to carrying out any of the experiments proposed herein is lack of a suitable instrument. The great increase in sensitivity over that of the Cary 61 or Jasco 20 of a decade ago arises largely from modulation through a piezo-elastic cell pumped at 50 kHz, rather than a Pockels cell at much lower frequency. As a result of being quite sensitive and stable, the instrument will be reliably used for kinetics work, with a time constant as low as 250 Musec; for stopped-flow kinetics, the dead time is 1 msec. Preliminary measurements of lysozyme interaction with poly(A) suggested that one could observe a process with a half-life of 5 msec. The data processor allows increased sensitivity over the offical specifications, through signal averaging and repetitive scanning. The instrument will produce real-time corrected and differential spectra. The 16K memory allows storage of 32 spectra or kinetics runs.